The present invention relates to crosslinked phenoxyphosphazene compounds, a process for the preparation thereof, flame retardants, flame-retardant resin compositions and moldings of flame-retardant resins.
Synthetic resins are widely used in various fields such as electric and electronic products, office automation equipment, office equipment and communications equipment because of their excellent molding processability, mechanical properties, appearance and the like. The resins used in certain applications are required to have flame retardancy for protection against the heat and ignition of internal parts in devices and appliances.
In order to impart flame retardancy to synthetic resins, a flame retardant is generally added to the resin prior to molding of the resin. Flame retardants are roughly classified into two groups, i.e., halogen-containing flame retardants and halogen-free flame retardants.
Examples of halogen-containing flame retardants include tetrabromobisphenol-A and like organic halogen compounds; tris(chloroethylphosphate), tris(2,3-dibromopropyl)phosphate and like halogen-containing organic phosphorus compounds. Halogen-containing flame retardants produce high flame-retardant effects but also reduce heat stability of matrix synthetic resins, cause deterioration and discoloration of the resins and further have the following drawbacks. Halogen-containing flame retardants undergo thermal decomposition to generate hydrogen halide, thereby causing corrosion of metallic molds, and further produce low molecular weight toxic halogen compounds as byproducts during molding or burning.
Examples of halogen-free flame retardants include magnesium hydroxide, aluminum hydroxide and like inorganic metal hydroxides; triphenyl phosphate (TPP), resorcinol bis(diphenylphosphate)(RDPP), trixylyl phosphate (TXP) and like organic phosphorus compounds (EP Patent No. 174,493, Dutch Patent No. 8,802,346, Japanese Unexamined Patent Publication No. 1,079/1993 and U.S. Pat. No. 5,122,556).
The inorganic metal hydroxides exhibit flame retardancy due to water generated by thermal decomposition. Since water merely produces low flame retardant effects, the inorganic metal hydroxide must be added in a large amount to provide a sufficient level of flame retardancy. However, such a large amount addition entails a disadvantage that the inherent properties of synthetic resins (e.g., mechanical properties) are impaired.
The organic phosphorus compounds produce comparatively high flame-retardant effects. However, since these compounds are liquid or low melting solid and have a high volatility, it is necessary to use a low temperature for molding a resin composition containing an organic phosphorus compound, and there always arise problems such as blocking during kneading, and migration of the organic phosphorus compound to the surface (juicing) during kneading or molding. Moreover, resin compositions containing said organic phosphorus compound have the drawback of dripping (falling of molten resin droplets) during burning and spreading of a fire due to the dripping. Consequently, in order to obtain a rating of V-0 (flaming does not continue for more than a specified period, and there are no molten resin drips which ignite cotton) in a flame retardancy test UL-94 (Testing for Flammability of Plastic Materials for Parts in Devices and Appliances, which is a standard test for evaluating flame retardancy), by adding an organic phosphorus compound to a resin, it is necessary to add a fluorine-containing resin such as polytetrafluoroethylene (PTFE) as an agent for preventing dripping of molten resin during burning. However, the fluorine-containing resin contains halogen and evolves toxic gases during combustion.
Known as flame retardants are phenoxyphosphazene compounds obtained by reacting dichlorophosphazene with a monohydroxy compound such as phenol. For example, proposed is adding a phenoxyphosphazene compound to a thermoplastic resin, such as polyamide resin (Japanese Examined Patent Publication No. 53,746/1981), polycarbonate resin (Japanese Unexamined Patent Publication No. 37,149/1976), polycarbonate or a mixture of polycarbonate and other thermoplasitic resins (Japanese Unexamined Patent Publication No. 292,233/1995) or a mixture of aromatic polycarbonate and rubber-styrene resin (Japanese Unexamined Patent Publication No. 53,009/1997), or to a thermosetting resin such as epoxy resin (Japanese Unexamined Patent Publication No. 225,714/1996).
Such incorporation of phenoxyphosphazene may increase the limit oxygen index (LOI) value (an index of flame retardancy) but does not impart sufficiently improved flame retardancy to the resin and inevitably reduces heat resistance and mechanical properties of the resin.
Further, Japanese Unexamined Patent Publication No. 47,042/1976 proposes using as a thermoplastic aromatic polyester flame retardant a phosphazene compound prepared by substituting chlorine atoms of dichlorophosphazene with monohydroxy compounds (e.g., alkali metal phenolate) so as to have a substitution degree of 3.9 to 6 (based on the dichlorophosphazene trimer) and further substituting the residual chlorine atoms with alkali metal diphenolate (e.g., an alkali metal salt of 4,4xe2x80x2-isopropylidene diphenol).
However, when the phosphazene compound prepared by the production method disclosed therein is incorporated into a thermoplastic resin such as polyester or polycarbonate, the molecular weight of the thermoplastic resin decreases and moldings of the resulting resin composition will have low mechanical properties and low heat resistance and fail to have a sufficiently high flame retardancy. This tendency becomes more evident with the lapse of time from the production of the resin moldings.
An object of the present invention is to provide a novel phosphazene compound which can greatly improve flame retardancy.
Another object of the invention is to provide a flame retardant which, when incorporated into a thermoplastic resin or a thermosetting resin, does not reduce the molecular weight of the resin and thus does not impair the mechanical properties or heat resistance of the resin.
A further object of the invention is to provide a process for preparing the foregoing phosphazene compound.
Other features of the present invention will become apparent from the following description.
The present inventors carried out extensive research to achieve the above objects, and finally succeeded in producing a new crosslinked phenoxyphosphazene compound which is useful as a flame retardant for synthetic resins, and completed the present invention.
According to the present invention, there is provided a crosslinked phenoxyphosphazene compound characterized in that:
at least one phosphazene compound selected from the group consisting of a cyclic phosphazene compound represented by the formula (1) 
xe2x80x83(wherein m is an integer of 3 to 25 and Ph is a phenyl group) and a straight- or branched-chain phosphazene compound represented by the formula (2) 
xe2x80x83(wherein X1 represents a group xe2x80x94Nxe2x95x90P(OPh)3 or a group xe2x80x94Nxe2x95x90P(O)OPh, Y1 represents a group xe2x80x94P(OPh)4 or a group xe2x80x94P(O)(OPh)2, and n is an integer of 3 to 10000 and Ph is as defined above)
is crosslinked with at least one crosslinking group selected from the group consisting of o-phenylene group, m-phenylene group, p-phenylene group and bisphenylene group represented by the formula (3) 
xe2x80x83(wherein A is xe2x80x94C(CH3)2xe2x80x94, xe2x80x94SO2xe2x80x94, xe2x80x94Sxe2x80x94 or xe2x80x94Oxe2x80x94 and z is 0 or 1);
(a) each of the crosslinking groups is interposed between the two oxygen atoms left after the elimination of phenyl groups from the phosphazene compound;
(b) the amount of the phenyl groups in the crosslinked compound is 50 to 99.9% based on the total amount of the phenyl groups in said phosphazene compound represented by the formula (1) and/or said phosphazene compound represented by the formula (2); and
(c) the crosslinked phenoxyphosphazene compound has no free hydroxyl groups in the molecule.
According to the present invention, there is provided a process for preparing the foregoing crosslinked phenoxyphosphazene compound which comprises the following steps:
at least one dichlorophosphazene compound selected from the group consisting of a cyclic dichlorophosphazene compound represented by the formula (4) 
xe2x80x83(wherein m is as defined above) and a straight- or branched-chain dichlorophosphazene compound represented by the formula (5) 
xe2x80x83(wherein X2 represents a group xe2x80x94Nxe2x95x90PCl3 or a group xe2x80x94Nxe2x95x90P(O)Cl, Y2 represents a group xe2x80x94PCl4 or a group xe2x80x94P(O)Cl2, and n is as defined above) is reacted with a mixture of alkali metal phenolate represented by the formula (6) 
xe2x80x83(wherein M is an alkali metal) and at least one diphenolate selected from the group consisting of alkali metal diphenolate represented by the formula (7) 
xe2x80x83(wherein M is as defined above) and alkali metal diphenolate represented by the formula (8) 
xe2x80x83(wherein A, z and M are as defined above); and
the resulting compound is further reacted with the alkali metal phenolate.
The crosslinked phenoxyphosphazene compound of the invention produces higher flame retardant effects than conventional non-crosslinked phenoxyphosphazene compounds and imparts high flame retardancy to thermoplastic resins or thermosetting resins.
The crosslinked phenoxyphosphazene compound of the invention which is free of halogen does not cause corrosion of metallic molds or deterioration or discoloration of resins during molding and does not produce any toxic gases such as hydrogen halide during combustion.
Furthermore, the crosslinked phenoxyphosphazene compound of the invention which has a low volatility does not necessitate using a low resin molding temperature and is free of shortcomings such as blocking during kneading, migration of the flame retardant to the surface (juicing) during kneading or molding, and dripping during burning.
The present inventors carried out research and found that the phosphazene compound prepared by the method disclosed in the foregoing Japanese Unexamined Patent Publication No. 47,042/1976 has residual free hydroxyl groups derived from the starting material alkali metal diphenolate in the molecule. The present inventors further found that when a phosphazene compound containing such free hydroxyl groups is incorporated into a thermoplastic resin such as polyester or polycarbonate, the free hydroxyl groups cause the reduction of the molecular weight of the resin, and moldings of the resulting resin composition will have inferior mechanical properties and heat resistance.
The crosslinked phenoxyphosphazene compound of the invention having no free hydroxyl groups in the molecule does not reduce the molecular weight of synthetic resins and thus does not impair molding processability of synthetic resins or mechanical properties (e.g., impact resistance) and heat resistance of synthetic resin moldings.
In this specification, xe2x80x9chaving no free hydroxyl groups in the moleculexe2x80x9d means that the amount of free hydroxyl groups is less than the detectable limit, when measured according to the acetylation method using acetic anhydride and pyridine as described on page 353 of Analytical Chemistry Handbook (revised 3rd edition, edited by Japan Analytical Chemistry Academy, published by Maruzen Book Store Co., Ltd., 1981). Herein the term xe2x80x9cdetectable limitxe2x80x9d means the minimum amount detectable as hydroxyl equivalents per gram of a test sample (crosslinked phenoxyphosphazene compound of the invention), more specifically 1xc3x9710xe2x88x926 hydroxyl equivalents/gram.
On analysis of the crosslinked phenoxyphosphazene compound of the invention by the foregoing acetylation method, the resulting amount includes the amount of hydroxyl groups in the residual phenol used as a starting material. Since the quantity of the starting material phenol can be determined by high speed liquid chromatography, the amount of free hydroxyl groups in the crosslinked phenoxyphosphazene compound can be precisely determined.
The present invention provides a flame retardant comprising the aforementioned crosslinked phenoxyphosphazene compound as an active ingredient.
The present invention further provides a flame-retardant resin composition comprising 100 wt. parts of a thermoplastic resin or a thermosetting resin and 0.1 to 100 wt. parts of the aforementioned flame retardant.
The present invention further provides a flame-retardant resin composition comprising 100 wt. parts of a thermoplastic resin or a thermosetting resin, 0.1 to 100 wt. parts of the aforementioned flame retardant and 0.01 to 50 wt. parts of an inorganic filler.
The present invention also provides a flame-retardant resin composition comprising 100 wt. parts of a thermoplastic resin or a thermosetting resin, 0.1 to 50 wt. parts of the aforementioned flame retardant, and 0.1 to 50 wt. parts of an organic phosphorus compound free of halogen.
The present invention further provides a flame-retardant resin composition comprising 100 wt. parts of a thermoplastic resin, 0.1 to 100 wt. parts of the aforementioned flame retardant and 0.01 to 2.5 wt. parts of a fluorine-containing resin.
Further, the present invention provides flame-retardant resin molded articles produced by molding any of the above flame-retardant resin compositions.
Crosslinked Phenoxyphosphazene Compounds
The crosslinked phenoxyphosphazene compounds of the invention can be obtained by a process comprising the following two steps:
at least one dichlorophosphazene compound selected from the group consisting of a cyclic dichlorophosphazene compound represented by the formula (4) and a straight- or branched-chain dichlorophosphazene compound represented by the formula (5) is reacted with a mixture of alkali metal phenolate represented by the formula (6) and at least one diphenolate selected from the group consisting of alkali metal diphenolate represented by the formula (7) and alkali metal diphenolate represented by the formula (8) (the first step); and
the resulting compound is further reacted with the alkali metal phenolate (the second step).
The study of the present inventors revealed that alkali metal diphenolate represented by the formula (7) or (8) reacts with dichlorophosphazene compounds much less than alkali metal phenolate represented by the formula (6). More specifically, when a mixture of a dichlorophosphazene compound and alkali metal phenolate represented by the formula (6) is heated, a phenoxyphospazene compound is produced by substitution of chlorine atoms with phenoxy groups. On the other hand, when a mixture of a dichlorophosphazene compound and alkali metal diphenolate represented by the formula (7) or (8) is heated, substitution reaction hardly proceeds.
Therefore, when a phenoxyphosphazene compound is prepared according to the method described in Japanese Unexamined Patent Publication No. 47,042/1976, which comprises reacting a dichlorophospazene compound with alkali metal phenolate and reacting the resulting compound with alkali metal diphenolate, it is highly difficult to completely substitute the chlorine atoms remaining after reaction, with alkali metal diphenolate. Even when one of the OM groups in the alkali metal diphenolate reacts with a chlorine atom in the dichlorophosphazene compound, the remaining OM group at the other end hardly reacts with a chlorine atom. When the OM group is converted to OH group, a hydroxyl-containing phosphazene compound results.
By contract, when a phenoxyphosphazene compound is prepared according to the method of the invention which comprises the steps of reacting a dichlorophosphazene compound with a mixture of alkali metal phenolate and alkali metal diphenolate and reacting the resulting compound with alkali metal phenolate, free hydroxyl groups do not remain in the molecule. M of both OM groups is eliminated from the alkali metal diphenolate so that the two oxygen atoms combine with phosphorus atoms in the dichlorophosphazene compound, thus giving a crosslinked phenoxyphosphazene compound (with an increased molecular weight).
The dichlorophosphazene compounds of the formula (4) and (5) for use as starting materials in the production process of the invention can be produced by known methods as described in Japanese Unexamined Patent Publication No. 87,427/1982, Japanese Examined Patent Publications Nos. 19,604/1983, 1363/1986 and 20,124/1987, etc. An exemplary method comprises reacting ammonium chloride and phosphorus pentachloride (or ammonium chloride, phosphorus trichloride and chlorine) at about 120 to 130xc2x0 C. using chlorobenzene as a solvent, followed by removal of hydrogen chloride. According to this method, dichlorophosphazene compounds of the formula (4) and (5) can be obtained as a mixture.
According to the present invention, this mixture can be used per se as a starting compound, or can be separated into a cyclic dichlorophosphazene compound of the formula (4) and a straight- or branched-chain dichlorophosphazene compound of the formula (5) and either of them can be used singly.
Of dichlorophosphazene compounds represented by the formula (5), those wherein n is an integer of 3 to 1000 are preferred.
Examples of alkali metal phenolates represented by the formula (6) include a wide range of those known, and are sodium phenolate, potassium phenolate, lithium phenolate and so on. These alkali metal phenolates can be used either alone or in combination.
There is no limitation on the positions of two xe2x80x94OM groups (wherein M is as defined above) in alkali metal diphenolate of the formula (7). Any of ortho, metha and para will do. Examples of alkali metal diphenolates include alkali metal salts of resorcinol, hydroquinone, catechol and the like, of which sodium salts and lithium salts are preferred. These alkali metal diphenolates can be used either alone or in combination.
Examples of alkali metal diphenolates represented by the formula (8) include alkali metal salts of 4,4xe2x80x2-isopropylidenediphenol (bisphenol-A), 4,4xe2x80x2-sulfonyldiphenol (bisphenol-S), 4,4xe2x80x2-thiodiphenol, 4,4xe2x80x2-oxydiphenol, 4,4xe2x80x2-diphenol or the like, of which sodium salts and lithium salts are preferred. Alkali metal diphenolates are used either alone or in combination.
According to the present invention, alkali metal diphenolate of the formula (7) and alkali metal diphenolate of the formula (8) can be used either alone or in combination.
In the first step according to the production process of the invention, it is desirable to use alkali metal phenolate and alkali metal diphenolate in such amounts that not all chlorine atoms in the dichlorophosphazene compound are consumed by the reaction with alkali metal phenolate and alkali metal diphenolate, namely, some chlorine atoms in the dichlorophosphazene compound remain as they are after the reaction with alkali metal phenolate and alkali metal diphenolate. Consequently, xe2x80x94OM groups (wherein M is as defined above) at both sides in alkali metal diphenolate combine with phosphorus atoms of the dichlorophosphazene compound. In the first step, the alkali metal phenolate and the alkali metal diphenolate are used usually in such amounts that the combined amount of both phenolates, relative to the chlorine content of the dichlorophosphazene compound, is about 0.05 to 0.9 equivalents, preferably about 0.1 to 0.8 equivalents.
In the second step according to the production process of the invention, it is desirable to use alkali metal phenolate in an amount such that chlorine atoms and free hydroxyl groups in the compound obtained by the first step can be all consumed by the reaction with alkali metal phenolate. According to the present invention, the alkali metal phenolate is used usually in an amount of about 1 to 1.5 equivalents, preferably about 1 to 1.2 equivalents, relative to the chlorine content of the dichlorophosphazene compound.
According to the present invention, the ratio of the alkali metal phenolate (the total amount thereof used in the first and second steps) and alkali metal diphenolate (alkali metal diphenolate/alkali metal phenolate, molar ratio) is usually about 1/2000 to 1/4, preferably 1/20 to 1/6.
The reactions in the first step and the second step are carried out in an organic solvent, usually at a temperature between room temperature and about 150xc2x0 C., preferably about 80 to 140xc2x0 C. Examples of useful organic solvents are aromatic hydrocarbons such as benzene, toluene and xylene; and halogenated aromatic hydrocarbons such as monochlorobenzene and dichlorobenzene. The reactions are completed usually in about 1 to 12 hours, preferably about 3 to 7 hours.
The crosslinked phenoxyphosphazene compound of the invention obtained by the above reactions can be easily isolated and purified from the reaction mixture by a conventional isolation method such as washing, filtration, drying or the like.
The decomposition temperature of the crosslinked phenoxyphosphazene compound of the invention is usually in the range of 250 to 350xc2x0 C.
The proportion of the phenyl groups in the crosslinked phenoxyphosphazene compound of the invention is 50 to 99.9%, preferably 70 to 90%, based on the total amount of the phenyl groups in the cyclic phenoxyphosphazene of the formula (1) and/or straight- or branched-chain phenoxyphosphazene of the formula (2).
The terminal groups X1 and Y1 in the formula (2) may vary in accordance with the reaction conditions and other factors. If the reaction is carried out under ordinary conditions, e.g., under mild conditions in a non-aqueous system, the resulting product will have a structure wherein X1 is xe2x80x94Nxe2x95x90P(OPh)3 and Y1 is xe2x80x94P(OPh)4. If the reaction is carried out under such conditions that moisture or an alkali metal hydroxide is present in the reaction system, or under so severe conditions that a rearrangement reaction occurs, the resulting product will have a structure wherein X1 is xe2x80x94Nxe2x95x90P(OPh)3 and Y1 is xe2x80x94P(OPh)4 and additionally a structure wherein X1 is xe2x80x94Nxe2x95x90P(O)OPh and Y1 is xe2x80x94P(O)(OPh)2.
The crosslinked phenoxyphosphazene compound of the invention is useful as a flame retardant for synthetic resins.
Flame-retardant Resin Composition
The flame-retardant resin composition of the present invention comprises a thermoplastic resin or a thermosetting resin, and the above crosslinked phenoxyphosphazene compound.
(a) Thermoplastic Resin
A wide variety of resins known in the art may be used as thermoplastic resin for use in the present invention. Such resins are, for example, polyethylene, polypropylene, polyisoprene, polyesters (polyethylene terephthalate, polybutylene terephthalate, etc.), polybutadiene, styrene resin, impact-resistant polystyrene, acrylonitrile-styrene resin (AS resin), acrylonitrile-butadiene-styrene resin (ABS resin), methyl methacrylate-butadiene-styrene resin (MBS resin), methyl methacrylate-acrylonitrile-butadiene-styrene resin (MABS resin), acrylonitrile-acrylic rubber-styrene resin (AAS resin), polymethyl (meth)acrylate, polycarbonate, modified polyphenylene ether (PPE), polyamide, polyphenylene sulfide, polyimide, polyether ether ketone, polysulfone, polyarylate, polyether ketone, polyether nitrile, polythioether sulfone, polyether sulfone, polybenzimidazol, polycarbodiimide, polyamideimide, polyetherimide, liquid crystalline polymer, composite plastics and the like.
Among these thermoplastic resins, polyester, ABS resin, polycarbonate, modified polyphenylene ether, polyamide, etc., are preferably used.
In the present invention, the thermoplastic resins may be used singly or in combination.
(b) Thermosetting Resin
A wide variety of resins known in the art may be used as the thermosetting resin for use in the present invention. Such thermosetting resins include polyurethane, phenol resin, melamine resin, urea resin, unsaturated polyester resin, diallyl phthalate resin, silicon resin and epoxy resin.
Among these thermosetting resins, particularly preferable are polyurethane, phenolic resin, melamine resin, epoxy resin, etc.
The epoxy resins are not limited to any specific types and may be selected from a wide variety of epoxy resins known in the art. Examples of such epoxy resins include bisphenol-A type epoxy resin, bisphenol-F type epoxy resin, bisphenol-AD type epoxy resin, phenol novolac type epoxy resin, cresol novolac type epoxy resin, cycloaliphatic epoxy resin, glycidyl ester-based resin, glycidyl amine-based epoxy resin, heterocyclic epoxy resin, urethane modified epoxy resin and brominated bisphenol-A type epoxy resin.
In the present invention, the thermosetting resins may be used singly or in combination.
The amount of the flame retardant (crosslinked phenoxyphosphazene compound of the invention) relative to the thermoplastic resin or thermosetting resin is not particularly limited, but is 0.1-100 wt. parts, preferably 1-50 wt. parts, more preferably 5-30 wt. parts, based on 100 wt. parts of the thermoplastic resin or thermosetting resin.
(c) Inorganic Filler
The flame-retardant resin composition of the present invention may contain inorganic fillers to further enhance dripping preventing effect.
Conventionally, these inorganic fillers have been used mainly as reinforcements for improving the mechanical properties of resins. However, the inventors of the present invention have found that said flame retardants and inorganic fillers, when both are present in a resin, act synergistically and therefore are effective for improving the flame-retardant effects of the flame retardant, especially dripping preventive effect, as well as the mechanical properties of the resin.
When said flame retardant and the inorganic filler are both present in a resin, the surface layer of the resin becomes dense and reinforced. This prevents the diffusion of gases formed during combustion, and induces the formation of a char layer from the flame retardant, resulting in high flame-retardancy.
The inorganic fillers may be known fillers for resins. Examples of such fillers include mica, kaolin, talc, silica, clay, barium sulfate, barium carbonate, calcium carbonate, calcium sulfate, calcium silicate, titanium oxide, glass beads, glass balloons, glass flakes, glass fibers, fibrous alkali metal titanates (potassium titanate fibers, etc.), fibrous transition metal borates (aluminum borate fibers, etc.), fibrous alkaline earth metal borates (magnesium borate fibers, etc.), zinc oxide whisker, titanium oxide whisker, magnesium oxide whisker, gypsum whisker, aluminum silicate (mineralogical name: mullite) whisker, calcium silicate (mineralogical name: wollastonite) whisker, silicon carbide whisker, titanium carbide whisker, silicon nitride whisker, titanium nitride whisker, carbon fibers, alumina fibers, alumina-silica fibers, zirconia fibers, quartz fibers and the like.
Among these inorganic fillers, it is preferred to use fillers having shape anisotropy such as fibrous fillers, e.g., fibrous alkali metal titanates, fibrous transition metal borates, fibrous alkaline earth metal borates, zinc oxide whisker, titanium oxide whisker, magnesium oxide whisker, aluminum silicate whisker, calcium silicate whisker, silicon carbide whisker, titanium carbide whisker, silicon nitride whisker, titanium nitride whisker, and mica. More preferable are fibrous alkali metal titanates, fibrous transition metal borates, fibrous alkaline earth metal borates, titanium oxide whisker, calcium silicate whisker and the like.
These inorganic fillers may be used singly or in combination.
Among these inorganic fillers, those having shape anisotropy such as whiskers and mica are preferably used.
Examples of the potassium titanate fibers among inorganic fillers include potassium hexatitanate fibers having an average fiber diameter of about 0.05-2 xcexcm and an average fiber length of about 1-500 xcexcm, and preferably having an aspect ratio (fiber length/fiber diameter) of 10 or greater. Among them, potassium hexatitanate fibers having a pH ranging from 6 to 8.5 are more preferable. A pH of potassium titanate fibers mentioned herein refers to a pH, as determined at 20xc2x0 C., of 1.0 wt. % of an aqueous suspension of potassium titanate fibers (in deionized water) which was stirred for 10 minutes. If the pH of the potassium titanate fibers is much higher than 8.5, physical properties of the resin and resistance to discoloration with heat may be disadvantageously decreased. On the other hand, when the pH is far below 6, the strength of the resulting resin composition is not effectively increased, and the residual acid may corrode processing machines and metallic molds. Hence it is not favorable.
The amount of the inorganic filler relative to the thermoplastic resin or thermosetting resin is not particularly limited. In view of a balance of improvements in mechanical properties and flame retardancy, however, the amount is 0.01-50 wt. parts, preferably 1-20 wt. parts, based on 100 wt. parts of the thermoplastic resin or thermosetting resin.
(d) Organic Phosphorus Compound Free of Halogen
The flame-retardant resin composition of the present invention may contain an organic phosphorus compound free of halogen (hereinafter referred to as xe2x80x9chalogen-free organic phosphorus compoundsxe2x80x9d) to further improve the flame retardancy thereof.
It is known that halogen-free organic phosphorus compounds are capable of improving the flame retardancy of the matrix such as resins. However, the inventors of the present invention found that when the specific phosphazene compounds for use in the present invention is used in combination with the halogen-free organic phosphorus compound, the flame-retardant effect is significantly increased due to synergism. The reason for this remarkable effect still remains to be elucidated. However, it is presumably because the conjoint use of these two compounds serves to form an expansion layer along with a char layer on the surface of the resin composition during combustion, and these layers suppress the diffusion of decomposition products and heat transfer.
A wide variety of halogen-free organic phosphorus compounds known in the art may be used in the present invention. For example, useful compounds include those disclosed in Japanese Examined Patent Publication No. 19003/1994, Japanese Unexamined Patent Publication No. 115262/1990, Japanese Unexamined Patent Publication No. 1079/1993, Japanese Unexamined Patent Publication No. 322277/1994, the specification of U.S. Pat. No. 5,122,556, etc.
Specific examples of the halogen-free phosphorus compound include trimethyl phosphate, triethyl phosphate, tributyl phosphate, trioctyl phosphate, triphenyl phosphate, tricresyl phosphate, trixylyl phosphate, cresyl diphenyl phosphate, xylyl diphenyl phosphate, tolyl dixylyl phosphate, tris(nonylphenyl) phosphate, (2-ethylhexyl)diphenyl phosphate and like phosphates; resorcinol diphenyl phosphate, hydroquinone diphenyl phosphate and like hydroxyl-containing phosphates; resorcinol bis(diphenyl phosphate), hydroquinone bis(diphenyl phosphate), bisphenol-A bis(diphenyl phosphate), bisphenol-S bis(diphenyl phosphate), resorcinol bis(dixylyl phosphate), hydroquinone bis(dixylyl phosphate), bisphenol-A bis(ditolyl phosphate), biphenol-A bis(dixylyl phosphate), bisphenol-S bis(dixylyl phosphate) and like condensed phosphate compounds; and trilauryl phosphine, triphenyl phosphine, tritolyl phosphine, triphenyl phosphine oxide, tritolyl phosphine oxide and like phosphine or phosphine oxide compounds.
Among these halogen-free organic phosphorus compounds, preferable are triphenyl phosphate, tricresyl phosphate, trixylyl phosphate, resorcinol bis(diphenyl phosphate), hydroquinone bis(diphenyl phosphate), bisphenol-A bis(diphenyl phosphate), resorcinol bis(dixylyl phosphate), hydroquinone bis(dixylyl phosphate), bisphenol-A bis(ditolyl phosphate) and like condensed phosphate compounds; and triphenyl phosphine oxide, tritolyl phosphine oxide and like phosphine oxide compounds. In particular, preferable are the compounds such as triphenyl phosphate, resorcinol bis(diphenyl phosphate), resorcinol bis(dixylyl phosphate), triphenyl phosphine oxide and the like.
These halogen-free organic phosphorus compounds may be used singly or in combination.
The amount of the halogen-free organic phosphorus compound relative to the thermoplastic resin or thermosetting resin is not particularly limited. In view of a balance of improvements in mechanical properties and flame retardancy, however, the amount of the halogen-free organic phosphorus compound is 0.1-50 wt. parts, preferably 1-30 wt. parts, based on 100 wt. parts of the thermoplastic resin or thermosetting resin. The amount of the flame retardant to be added thereto is 0.1-50 wt. parts, preferably 5-30 wt. parts, based on 100 wt. parts of the thermoplastic resin or thermosetting resin.
(e) Fluorine-containing Resin
Further, a fluorine-containing resin may be incorporated into the flame-retardant resin composition of the present invention containing a thermoplastic resin as a matrix within the range which does not adversely affect the object of the present invention. The amount of the fluorine-containing resin to be used is not particularly limited, but is 0.01-2.5 wt. parts, preferably 0.1-1.2 wt. parts, based on 100 wt. parts of the thermoplastic resins.
A wide variety of fluorine-containing resins known in the art may be used in the present invention. The examples include polytetrafluoroethylene resin (PTFE), tetrafluoroethylene-hexafluoropropylene copolymer resin (FEP), tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer resin (PFA), tetrafluoroethylene-ethylene copolymer resin (ETFE), polychlorotrifluoroethylene resin (CTFE) and polyvinylidene fluoride (PVdF). Among these, PTFE is particularly preferable. By the addition of the fluorine-containing resins, the dripping preventing effect is produced in a more pronounced manner.
(f) Other Additives
The flame-retardant composition of the invention is a resin composition which does not contain a halogen (e.g., chlorine, bromine)-containing compound as a flame retardant component but can produce excellent flame retardant effects. One or more flame retardant additives conventionally used may be incorporated into the composition insofar as they do not adversely affect the excellent effects.
The flame retardant additive for use is not limited, and usually any additive that produces flame retardant effects can be used. Examples of useful flame retardant additives are metal oxides such as zinc oxide, tin oxide, iron oxide, molybdenum oxide, copper oxide and manganese dioxide; metal hydroxides such as aluminum hydroxide, magnesium hydroxide, zirconium hydroxide, oxalic acid-treated aluminum hydroxide and nickel compound-treated magnesium hydroxide; alkali metal salts or alkaline earth metal salts such as sodium carbonate, calcium carbonate, barium carbonate and sodium alkylsulfonate; organic chlorine compounds or organic bromine compounds such as chlorinated paraffin, perchlorocyclopentadecane, tetrabromobisphenol-A; epoxy resins, bis(tribromophenoxy)ethane and bis(tetrabromophthalimino)ethane; antimony compounds such as antimony trioxide, antimony tetraoxide, antimony pentaoxide and sodium antimonate; red phosphorus, halogen-containing phosphoric ester compounds, halogen-containing condensed phosphoric ester compounds or phosphonic acid ester compounds, nitrogen-containing compounds such as melamine, melamine cyanurate, melamine phosphate, melam, melem, mellon, succinoguanamine, guanidine sulfamate, ammoninum sulfate, ammonium phosphate, ammonium polyphosphate and alkylamine phosphate; boron compounds such as zinc borate, barium methaborate and ammonium borate; silicon compounds such as silicone polymers and silica; and thermally expansive graphite.
These flame retardant additives can be used singly or in combination.
Further, one or more conventional resin additives may be incorporated into the flame-retardant composition of the invention, insofar as they do not adversely affect the excellent properties. Examples of useful resin additives include flame retardants other than the aforementioned ones, dripping inhibitors (dropping inhibitors), UV absorbers, light stabilizers, antioxidants, light screens, metal deactivators, quenching agents, heat resistance stabilizers, lubricants, mold releasing agents, coloring agents, antistatic agents, antiaging agents, plasticizers, impact strength improving agents and compatibilizers.
The UV absorber is a component for absorbing light energy and releasing the absorbed light energy harmlessly in the form of heat energy by the transformation thereof into a keto form through intramolecular proton transfer (in the case of benzophenones and benzotriazoles) or by cis-trans isomerization (in the case of cyanoacrylates). Specific examples of UV absorbers include 2-hydroxybenzophenones such as 2,4-dihydroxybenzophenone, 2-hydroxy-4-methoxybenzophenone, 2-hydroxy-4-octoxybenzophenone and 5,5xe2x80x2-methylenebis(2-hydroxy-4-methoxybenzophenone); 2-(2xe2x80x2-hydroxyphenyl)benzotriazoles such as 2-(2xe2x80x2-hydroxy-5xe2x80x2-methylphenyl)benzotriazole, 2-(2xe2x80x2-hydroxy-5xe2x80x2-t-oetylphenyl)benzotriazole, 2-(2xe2x80x2-hydroxy-3xe2x80x2,5xe2x80x2-di-t-butylphenyl)benzotriazole, 2-(2xe2x80x2-hydroxy-3xe2x80x2,5xe2x80x2-di-t-butylphenyl)-5-chlorobenzotriazole, 2-(2xe2x80x2-hydroxy-3xe2x80x2-t-5xe2x80x2-methylphenyl)-5-chlorobenzotriazole, 2-(2xe2x80x2-hydroxy-3xe2x80x2,5xe2x80x2-dicumylphenyl)benzotriazole and 2,2xe2x80x2-(methylenebis(4-t-octyl-6-benzotriazolyl)phenol; benzoates such as phenylsalicylate, resorcinol monobenzoate, 2,4-di-t-butylphenyl-3xe2x80x2,5xe2x80x2-di-t-butyl-4xe2x80x2-hydroxybenzoate and hexadecyl-3,5-di-t-butyl-4-hydroxybenzoate; and substituted oxalic anilide such as 2-ethyl-2xe2x80x2-ethoxy oxalic anilide and 2-ethoxy-4xe2x80x2-dodecyl oxalic anilide; cyanoacrylates such as ethyl-xcex1-cyano-xcex2,xcex2-diphenylacrylate and methyl-2-cyano-3-methyl-3-(p-methoxyphenyl)acrylate.
The light stabilizer is a component for decomposing hydroperoxides produced by light energy into stable Nxe2x80x94Oxc2x7radical, Nxe2x80x94OR or Nxe2x80x94OH, thereby providing light stability. For example, hindered amine light stabilizers can be used. Specific examples of light stabilizers include 2,2,6,6-tetramethyl-4-piperidylstearate, 1,2,2,6,6-pentamethyl-4-piperidylstearate, 2,2,6,6-tetramethyl-4-piperidylbenzoate, bis(2,2,6,6-tetramethyl-4-piperidylsebacate, bis(1,2,2,6,6-pentamethyl-4-piperidyl)sebacate, tetrakis(2,2,6,6-tetramethyl-4-piperidyl)-1,2,3,4-butane tetracarboxylate, tetrakis(1,2,2,6,6-pentamethyl-4-piperidyl)-1,2,3,4-butanetetracarboxylate, bis(1,2,2,6,6-pentamethyl-4-piperidyl)-di(tridecyl)-1,2,3,4-butanetetracarboxylate, bis(1,2,2,6,6-pentamethyl-4-piperidyl)-2-butyl-2-(3xe2x80x2,5xe2x80x2-di-t-butyl-4-hydroxybenzyl)malonate, 1-(2-hydroxyethyl)-2,2,6,6-tetramethyl-4-piperidinol/diethyl succinate polycondensate, 1,6-bis(2,2,6,6-tetramethyl-4-piperidylamino)hexane/dibromoethane polycondensate, 1,6-bis(2,2,6,6-tetramethyl-4-piperidylamino)hexane/2,4-dichloro-6-t-octylamino-s-triazine polycondensate, 1,6-bis(2,2,6,6-tetramethyl-4-piperidylamino)hexane/2,4-dichloro-6-morpholino-s-triazine polycondensate, and the like.
The antioxidant is a component for stabilizing peroxide radicals, such as hydroperoxy radicals, which are formed upon heat with molding or light exposure, or for decomposing generated peroxides, such as hydroperoxides. Examples of antioxidants include hindered phenol type antioxidants and peroxide decomposers. The hindered phenol type antioxidant acts as a radical chain-transfer inhibitor, and the peroxide decomposer decomposes peroxides generated in the reaction system into a stable alcohol, and prevents autoxidation.
Specific examples of hindered phenol type antioxidants include 2,6-di-t-butyl-4-methylphenol, styrenated phenol, n-octadecyl-3-(3,5-di-t-butyl-4-hydroxylphenyl)propionate, 2,2xe2x80x2-methylene bis(4-methyl-6-t-butylphenol), 2-t-butyl-6-(3-t-butyl-2-hydroxy-5-methylbenzyl)-4-methylphenylacrylate, 2-[1-(2-hydroxy-3,5-di-t-pentylphenyl)ethyl]-4,6-di-t-pentylphenylacrylate, 4,4xe2x80x2-butylidene bis(3-methyl-6-t-butylphenol), 4,41-thiobis(3-methyl-6-t-butylphenol), alkylated bisphenol, tetrakis[methylene-3-(3,5-di-t-butyl-4-hydroxyphenyl)proprionate]methane, 3,9-bis[2-{3-(3-t-butyl-4-hydroxy-5-methylphenyl)propionyloxy}-1,1-dimethylethyl]-2,4,8,10-tetraoxaspiro[5.5]undecane, and the like.
Examples of peroxide decomposers include organic phosphorus type peroxide decomposers such as tris(nonylphenyl)phosphite, triphenyl phosphate and tris(2,4-di-t-butylphenyl)phosphite; and organic thio type peroxide decomposers such as dilauryl-3,3xe2x80x2-thiodipropionate, dimyristyl-3,3xe2x80x2-thiodipropionate, distearyl-3,3xe2x80x2-thiodipropionate, pentaerythrityltetrakis(3-laurylthiopropionate), ditridecyl-3,3xe2x80x2-thiodipropionate and 2-mercaptobenzimidazole.
The light screen is a component for preventing light from penetrating into the bulk of a polymer. Specific examples of light screens include titanium oxide having a rutile structure (TiO2), zinc oxide (ZnO), chromium oxide (Cr2O3) and cerium oxide (CeO2).
The metal deactivator is a component for deactivating heavy metal ions in the resin by forming a chelate compound. Specific examples of metal deactivators include benzotriazoles and derivatives thereof (e.g. 1-hydroxybenzotriazole and the like).
The quenching agent is a component for deactivating photo-excited hydroperoxides and functional groups such as carbonyl groups in the polymer due to energy transfer. Useful quenching agents include organic nickel and the like.
In order to impart improved antifogging, antifungal, antimicrobial or like properties, other conventionally known additives may also be added.
Production of Flame-retardant Resin Compositions of the Invention
The flame-retardant resin composition of the invention can be produced by mixing a thermoplastic resin or a thermosetting resin and the aforementioned frame retardant, optionally together with an inorganic filler, a halogen-free organic phosphorus compound, a fluorine-containing resin, one or more flame retardant additives and other additives, in prescribed or proper amounts, followed by mixing and kneading the.mixture by a conventional method. For example, the mixture of components in the form of powder, beads, flakes or pellets is kneaded using an extruder, e.g., a uniaxial extruder or a biaxial extruder, or a kneader, e.g., Banbury mixer, a pressure kneader or a two-roll mill, giving a resin composition of the invention. When a liquid needs to be added, a conventional liquid injection device can be used and the mixture can be kneaded using the aforementioned extruder, kneader or the like.
Flame-retardant Resin Moldings of the Invention
The flame-retardant resin composition of the invention can be molded into flame-retardant resin moldings. For example, the resin composition can be molded into resin plates, sheets, films, special shapes or like extrusion moldings of various shapes using a conventional molding method such as press molding, injection molding or extrusion molding, or can be molded into a resin plate of two- or three-layered structure using a coextruder.
The thus-obtained flame-retardant resin composition and flame-retardant resin moldings of the invention can find wide application in various industrial fields, such as electrical, electronics or telecommunication industries, agriculture, forestry, fishery, mining, construction, foods, fibers, clothing, medical services, coal, petroleum, rubber, leather, automobiles, precision machinery, timber, furniture, printing, musical instruments, and the like.
Stated more specifically, the flame-retardant resin composition and flame-retardant resin moldings of the invention can be used for business or office automation equipment, such as printers, personal computers, word processors, keyboards, PDA (personal digital assistants), telephones, facsimile machines, copying machines, ECR (electronic cash registers), desk-top electronic calculators, electronic databooks, electronic dictionaries, cards, holders and stationery: electrical household appliances and electrical equipment such as washing machines, refrigerators, cleaners, microwave ovens, lighting equipment, game machines, irons and kotatsu (low, covered table with a heat source underneath); audio-visual equipment such as TV, VTR, video cameras, radio cassette recorders, tape recorders, mini discs, CD players, speakers and liquid crystal displays; and electric or electronic parts and telecommunication equipment, such as connectors, relays, condensers, switches, printed circuit boards, coil bobbins, semiconductor sealing materials, electric wires, cables, transformers, deflecting yokes, distribution boards, and clocks and watches.
Further, the flame-retardant resin composition and flame-retardant resin moldings of the invention can be widely used for the following applications: materials for automobiles, vehicles, ships, aircraft and constructions, such as seats (e.g., padding, outer materials), belts, ceiling covering, convertible tops, arm rests, door trims, rear package trays, carpets, mats, sun visors, wheel covers, mattress covers, air bags, insulation materials, hangers, hand straps, electric wire coating materials, electrical insulating materials, paints, coating materials, overlaying materials, floor materials, corner walls, deck panels, covers, plywood, ceiling boards, partition plates, side walls, carpets, wall papers, wall covering materials, exterior decorating materials, interior decorating materials, roofing materials, sound insulating panels, thermal insulation panels and window materials; and living necessities and sporting goods such as clothing, curtains, sheets, plywood, laminated fiber boards, carpets, entrance mats, seats, buckets, hoses, containers, glasses, bags, cases, goggles, skies, rackets, tents and musical instruments.
The present invention will be specifically described below with reference to Synthesis Examples, Examples, Comparative Examples and Reference Examples, wherein parts and % mean weight parts and weight %, respectively. In addition, xe2x80x94Ph and xe2x80x94Phxe2x80x94 mean phenyl group and phenylene group, respectively. The evaluations in the Examples were carried out by the following methods.
1. Heat distortion temperature: Measured according to ASTM D-648 at a load of 18.6 kgf/cm2, and used as an index of heat resistance.
2. Flame retardancy: Evaluated according to the test method of UL-94 (Test for Flammability of Plastic Materials for Parts in Devices and Appliances UL94, Fourth Edition), using test specimens each measuring {fraction (1/16)} inch thick, 5 inches long and 0.5 inches wide.
Definitions in UL 94 are as follows.
The material classification are specified as follows:
94V-0
Afterflame time for each individual specimen t1 or t2: xe2x89xa610 sec.
Total afterflame time for any condition set (t1 plus t2 for the 5 specimens): xe2x89xa650 sec.
Afterflame plus afterglow time for each individual specimen after the second flame application (t2+t3): 30xe2x89xa6sec.
Afterflame or afterglow of any specimen up to the holding clamp: No
Cotton indicator ignited by flaming particles or drops: No
94V-1
Afterflame time for each individual specimen t1 or t2: xe2x89xa630 sec.
Total afterflame time for any condition set (t1 plus t2 for the 5 specimens): xe2x89xa6250 sec.
Afterflame plus afterglow time for each individual specimen after the second flame application (t2 or t3): xe2x89xa660 sec.
Afterflame or afterglow of any specimen up to the holding clamp: No
Cotton indicator ignited by flaming particles or drops: No
94V-2
Afterflame time for each individual specimen t1 or t2: xe2x89xa630 sec.
Total afterflame time for any condition set (t1 plus t2 for the 5 specimens): xe2x89xa6250 sec.
Afterflame plus afterglow time for each individual specimen after the second flame application (t2+t3): xe2x89xa660 sec.
Afterflame or afterglow of any specimen up to the holding clamp: No
Cotton indicator ignited by flaming particles or drops: Yes
3. Generation of volatile gas and discoloration at the time of molding: Inspected visually.
The thermoplastic resins, halogen-free organic phosphoric compounds and fluorine-containing resins used were as follows.